Fuel burner control system



Dec. 19, 1967 LUFT FUEL BURNER CONTROL SYSTEM Filed Aug. 25, 1966 PHOTOCELL FROM FUEL SUPPLY RECYCLE Tl M E HIGH -FIRE INVENTOR. ALFRED N. LUFT ATTORNEYS United States Patent 3,358,735 FUEL BURNER CONTROL SYSTEM Alfred Nathan Luft, Sarasota, Fla., assignor to Sun-Ray Burner Manufacturing Corporation, Jamaica, N.Y., a corporation of New York Filed Aug. 25, 1966, Ser. No. 575,014 Claims. (Cl. 15828) ABSTRACT OF THE DISCLOSURE A control system for a fuel burner having a nozzle, a source of fuel under pressure, and a means for igniting the fuel when issuing from the burner nozzle. This control system includes a fuel pump for providing a supply of fuel from a fuel source to the burner nozzle. A relay control structure is connected to an electrical power source and has a pair of output terminals. A valve means is in the circuit of the relay control structure and operates in response thereto for controlling the fuel pump to selectively provide a first level of fuel flow to the burner nozzle corresponding to a low-fire burning condition and a second level of fuel flow to the burner nozzle greater than the first level and corresponding to a high-fire burner condition. An ignition transformer is selectively connected to an electrical power source and has a pair of output terminals for providing a voltage to energize the fuel ignition means. A fail safe means is operative to permit the establishment of the high-fire burner condition only upon prior establishment of the low-fire burner condition, this fail safe means including a flame detection means for detecting the low-fire condition. The fuel pump has first and second suction inputs and a pressure output, and an input fuel line is connected between the source of fuel to the first suction input while an output fuel line is connected to the pressure output. A feedback fuel line is connected between the output fuel line and the second suction input, and a nozzle fuel line is connected to the burner nozzle from the junction of the output fuel line and the feedback fuel line. The valve means which is in the circuit of the relay control has a first normally closed valve which is disposed in the feedback line, and this first valve operates in response to the relay control so as to selectively vary the magnitude of fuel flow from the output fuel line to the second suction input. A second valve of the valve means is disposed in the nozzle fuel line to selectively vary the magnitude of fuel fiow from the output fuel line to the burner nozzle, so as to control in this way the magnitude of the burner flame.

This invention relates to a burner control system and more particularly to an automatic fuel burner relay control system.

In fuel burner systems for reasons of safety, fuel economy and equipment maintenance, before a full high level burner fire is initiated it is generally desirable to ensure that optimum operating conditions such as fuel supply, ignition and air supply have been fully established and properly stabilized and that the various system components are operating satisfactorily. Accordingly, it is advantageous to produce a preliminary low fire burner flame by providing an initial reduced fuel flow to the burner to be followed by the full fuel flow if all operating conditions are proved to be satisfactory during the low-fire stage. Furthermore, it is desirable todelay the initiation of the low fire stage, to accommodate the time 3,358,735 Patented Dec. 19, 1967 delay corresponding to the time required for various operating conditions to become fully established such as full speed of the fuel pump motor, buildup of adequate hydraulic pressure in the fuel lines and air supply to the fuel burner. When the fuel burner system is shut off after operating in a full fire condition, it is necessary to inhibit the restarting of the system until the expiration of a preselected period of time suificient to allow the heat sensitive relays in the burner control system to reset their contacts to their normal conditions.

In presently available fuel burner control systems, in order to achieve automatic fuel supply control it has been found necessary to resort to complicated circuitry requiring the use of complex and expensive components which often require maintenance.

It is therefore an object of the present invention to provide an economical automatic fuel burner control system, which provides for a low fire and high fire stage while utilizing standard and inexpensive control components.

An important feature of the present invention resides in the provision of a fuel burner control system wherein selective control of the burner flame is accomplished by singular control of the flow of fuel to the burner nozzle. Accordingly, the preferred embodiment of the present invention, as hereinafter described, is particularly useful in a constant air flow burner system, in which the lowfire condition utilizes the same magnitude of air flow as in the high fire condition.

In fuel burner systems because of the possibility of misoperation of the fuel supply or ignition apparatus there are presented serious inherent hazards such as explosion or fire. Accordingly it is important to provide fail safe means to insure that the various stages in the firing cycle are not initiated unless the prerequisite operating conditions are fully established and that a failure in the burner control system cause the supply of fuel to the burner to be interrupted.

It is therefore a further object of the present invention to provide an automatic fuel burner control system having a high system reliability together with a fail-safe capability.

In accordance With the principles of the present invention there is provided a fuel burner control circuit comprising a fuel burner having at least one burner nozzle, fuel pump means for providing a selectively variable flow of fuel from the fuel pump means to the burner nozzle, and fuel ignition means for igniting the fuel emanating from the burner nozzle. Relay control means, operative to control the ignition of fuel provided at the burner nozzle, are adapted for connection to an electrical power source to energize the control system. Valve means for control of the fuel pump means is provided and is operative in response to the relay control means to selectively vary the fuel supply to the burner nozzle to thereby provide a flame at the burner nozzle in accordance with a predetermined and selectively variable firing program comprising a low fire stage and a high fire stage.

The features of the invention which are believed to be novel are set forth with particularity in the appended claims. The invention, itself, however, both as to its organization and method of operation, together with further objects and features thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic diagram depicting the relay control circuit as well as the hydraulic circuit for fuel control.

FIG. 2 is a firing sequence diagram depicting the various stages in the firing cycle and the corresponding period of activation of the fuel pump motor, ignition transformer, and the fuel supply control valves.

Referring to FIG. 1 there is shown a relay arrangement for initiating and terminating successive stages in the firing cycle by selectively controlling the supply of fuel to the burner nozzle and the ignition thereof. Referring to FIG. 2 there is a diagram showing the order of occurrence and approximate duration of successive stages in the firing cycle. When it is desired to start up the system, it is necessary to delay the supply of fuel to the burner nozzle in order to provide sufficient time for normal operating conditions such as full speed of the fuel pump motor, sufficient fuel hydraulic pressure in the fuel lines and adequate flow of air to the burner to be established. This stage is known as the pre-purge stage and is approximately 6 seconds in duration.

Upon termination of the prepurge stage it is desired to provide a low flame at the burner nozzle before initiating the full high fire, in order to establish the system and to ensure that all the system components such as fuel and air supply as well as ignition components are functioning properly. This stage in the firing cycle is known as the low fire stage and is approximately 40 seconds in duration.

If all operating conditions are satisfactory during the low fire stage, the system will proceed to the high fire stage which will provide a full scale flame by supplying an increased flow of fuel to the burner nozzle. If a flame fails to be ignited or is insuflicient during the low fire cycle, the present system provides suitable flame detection means to initiate automatic shutdown of the system by cutting off the supply of fuel to the burner. The high fire cycle will continue until the system is turned off as desired. After the system is turned off, there is provided a recycle stage during which time the fuel burner cannot be started up again. The duration of the recycle stage, which lasts roughly about 75 seconds within a wide range of variation, corresponds to the time necessary for the various heat responsive elements in the system to cool down to ambient temperature and to, accordingly, reset the switching elements operative in response thereto, to their start up condition.

The supply of fuel is generally illustrated by the hydraulic circuit in FIG. 1 as comprising a fuel pump 42 driven by motor 60 and a pressure regulator valve 44 which may be adjusted to provide a pre-selected fuel pressure fiow eg 300 psi The fuel is provided by main fuel line 46 which delivers fuel from a fuel supply (not shown), the fuel flowing through line 46 into one of the suction sides 47 of fuel pump 42. Pressure relief valve 50 is operative to provide a pro-selected pressure of fuel at the junction of valve 50 and line 48, thereby controlling the fuel pressure at normally closed output valve 54 which controls the output of fuel to the burner nozzle as shown. Valves 54 and 52 are respectively controlled by solenoid coils 56 and 58 as hereinafter described. During the prepurge stage of the cycle, normally closed output valve 54 remains closed, while normally closed valve 52 is fully open, and accordingly, there is established a fuel feedback flow from pressure side 45, through line 48, pressure relief valve 50, feedback valve 52, line 53 and back to suction side 43. During this pre-purge period there is no output fuel flow to the burner nozzle because normally closed output valve 54 is closed.

When the low-fire stage is established, normally closed output valve 54 is opened, by virtue of the energization of solenoid 56 as hereinafter explained, while valve 52 remains open. Accordingly, the flow of fuel in line 48 divides into a feedback flow through feedback valve 52 as indicated above and a small output flow through opened output valve 54 to the burner nozzle.

Upon the commencement of the high-fire stage, feedback valve 52 is closed in response to the de-energization of solenoid 58 as hereinafter described, while output valve 54 remains open. Accordingly, there is no feedback fuel flow through valve 52 and the full fuel flow from pressure end through line 48 proceeds through opened output valve 54, output line and to the burner nozzle. Output valve 54 will remain open during the high-fire cycle providing a full fuel flow to the burner nozzle until the system is shut off, whereupon normally closed valve 54 is closed due to the deenergization of solenoid 56 as hereinafter described.

A relay control circuit is provided to control the supply of fuel to the burner at the various stages in the firing cycle and comprises a relay arrangement as follows. Motor relay coil 28 controls the initial supply of fuel to the burner: flame relay coil 33 is operative in response to cadmium cell 36 which detects the low fire flame to signal that satisfactory low fire conditions are obtained; safety relay heater 38 is operative in conjunction with flame relay 33 to insure that the high fire cycle is not initiated unless cadmium cell 36 has detected the prerequisite low fire flame and thereby causes flame relay coil 33 to become energized, and high-fire and scavenger relay heater 40 is operative to control the application of a full fuel flow to the burner upon the establishment of full fire conditions.

Referring to FIG. 1, the electrical circuit which provides automatic control of fuel flow and ignition is arranged as follows. A pair of line conductors 10 and 12 are connected at their respective terminals 14 and 16 to a. suitable AC. power source (not shown) to provide an AC. voltage across primary winding 18 of transformer 20. Center tap 32 of secondary winding 22 is connected to contacts 28-1 of motor relay 28, with the other ends of contacts 28-1 being connected to normally closed contacts 40-1 of high fire relay 40. Motor relay coil 28 interconnects contacts 38-1 and terminal 21 of thermostat switch 24 via lead 30 with the other terminal 27 being connected to one end of secondary winding 22 by leads 26 and 23. Flame relay switch 33-1 comprises a pole 74 which is operative to make contact with cold contact 66 when flame relay coil 33 is deenergized, and to make contact with hot contact 70 when relay coil 33 is energized. Safety relay heater 38 is connected at one end to the junction of contacts 28-1 and 40-1, and at the other end to cold contact 66. The opposite hot contact 70 is connected to the series arrangement of motor relay contacts 28-2 and high fire and scavenger relay heater 40 which is connected at its other end to the junction of contacts 40-1 and 38-1. Flame relay coil 33 is connected at one end to the junction of secondary winding 22 and pole 74 and at its other end via lead 35 to terminal 76 of cadmium cell 36, the other cadmium cell terminal 78 being connected to the junction of leads 23 and 26. Motor relay contacts 28-3 are connected at one end to line 12, and the other end to high fire contacts 40-2, with the other end of contacts 40-2 being connected to solenoid coil 58 which controls valve 52. Solenoid coil 56, which controls valve 54, is in series with its associated thermistor 92, with the other end of thermistor 92 being connected to the junction of contacts 29-3 and 40-2. Relay 96, which is provided to control the operation of pump motor 60 and ignition transformer 61, has its relay coil 98 connected between the junction of contacts 28-3 and 40-2, and the junction of solenoids 56 and 58, and one terminal of motor 60. Normally open contacts 98-1 which are operative to close in response to the energization of relay coil 98, are connected between the other terminal of motor 60 and line 12. Transformer 61 which provides the proper voltage for providing a fuel ignition spark is in parallel arrangement with pump motor 60.

The following is a description of the sequence of events in a fiiring cycle and will serve to explain the operation of the control system. Assuming that AC. power is being applied across terminals 14 and 16, when room thermostat 24 is energized by virtue of the ambient temperature, or thermostat switch 25 is closed by other starting means, motor relay coil 28 will be energized by a current which flows through a series path comprising winding 22, leads 23 and 26, closed switch 25, lead 30, motor relay coil 28, normally closed contacts 40-1 and 38-1, safety relay heater 38, contact 66, pole 74 and thence to the other end of secondary winding 22. As a result of the aforementioned energizing of motor relay coil 28, motor relay contacts 28-1, 28-2, and 28-3 will be closed. By virtue of the closing of motor relay contacts 28-3, relay coil 98 will be energized by current flowing through a series circuit comprising contacts 28-3, relay coil 98, lead 83 to line 10. The energization of relay coil 98 causes its associated contacts 98-1 to close, thus applying the source voltage, at terminals 14 and 16, across both pump motor 60 and ignition transformer 61, by means of lead 80, closed contacts 98-1 and lead 83.

It will be noted that the closing of contacts 98-1 also provides an energizing current path for solenoid 56, comprising lead 83, solenoid coil 56, thermistor 92 and closed contacts 28-3. However, thermistor 92 is designed to provide a six second delay before solenoid 56 is fully energized and accordingly, for about six seconds after the initiation of the pre-purge stage of the firing cycle as shown in FIG. 2, only valve 52 is opened, thus allowing a six second period for establishing the normal operating conditions of the system, such as full speed of motor 60, proper fuel pressurein pump 42, and proper air delivery.

After the aforementioned six second time lag, by virtue of the current passing therethrough, the resistance of thermistor 92 will decrease sufficiently and allow adequate energizing current to pass through solenoid 56 to open valve 54. Accordingly, the low fire stage is initiated and there is provided a fuel flow through valve 54 and line 55 to the burner nozzle (not shown) at the pressure preselected by pressure relief valve 50, e.g. typically 125 to 150 p.s.i. The remaining fuel flow from line 48 passes through valve 52 in accordance with the pre-selected setting of pressure relief valve 50, and is re-circulated through feedback line 53 back into pump 42 at its second suction end 43. There is thus established a low-fire flame at the burner nozzle.

In order to be assured that proper fuel flow and air supply conditions obtain, together with proper igniti'on, cadmium cell 36 is disposed in proximity to the burner flame to detect light emitted by the burner flame. Cadmium cell 36 is operative, in accordance with well known principles, to lower its resistance in accordance with the amount of light impinging thereon. Considering the series circuit comprising secondary winding 22, flame relay coil 33, and cadmium cell 36, it is seen that the voltage developed across winding 22 is apportioned between coil 33 and cell 30 in inverse proportion to their respective impedences. When there is insuflicient light impinging on cell 36, its resistance is high and hence only a small voltage will appear across coil 33, which is insuflicient to cause its energization. However, when the impedance of cell 36 is sufliciently reduced by virtue of the light produced by the burner flame, a proportionately greater voltage will appear across coil 33, increasing the current flow therethrough sufiiciently to pull its related pole 74 from the cold contact 66 to hot contact 70.

' Safety heater relay filament 38 is operative to heat up sufliciently within a predetermined time, e.g. 15 seconds, to open its corresponding contacts 40-1. Within this safety heater heating period, however, if proper low fire flame'conditions have been established, cadmium cell 36 will have detected sufiicient light from the burner flame to cause flame relay coil 33 to be energized, thus moving pole 74 from cold contact 66 to hot contact 70, thereby interrupting the energizing circuit for safety heater 38 comprising, the voltage developed across the left hand portion of secondary winding 22, pole 74, contact 66, safety heater filament 38 and motor relay coil contacts 28-1, and hence maintaining safety contacts 38-1 in their normally closed condition. On the other hand, if the burner flame is absent or is insuflicient to adequately lower the resistance of cadmium cell 36 and thereby cause pole 74 to be switched to hot contact 70 within the heating period of safety heater 38, pole 74 will remain in contact with cold contact 66, thus allowing safety heater 38 to sufliciently heat up to open safety relay contacts 38-1, thus de-energizing motor relay coil 28 and shutting off the system.

When pole 74 makes contact with hot contact 70, as explained above, high fire and scavenger heater 40 will be energized through the circuit path consisting of, secondary winding 22 having an A.C. voltage thereacross, pole 74, contact 70, motor relay contacts 28-2 (which are closed by virtue of the energization of motor relay coil 28 through contact 28-1, normally closed scavenger contacts 40-1 and normally closed safety contacts 38-1), high fire and scavenger heater 40, safety contacts 38-1, coil 28, thermostatic switch 25, line 26 and line 23 back to winding 22. Heater 40 will be sufliciently heated up to open its normally closed contact pairs 40-1 and 40-2, typically in about 45 seconds after the switching of pole 74 to hot contact 70, to thereby signal the beginning of the high fire stage and produce the following sequence of events.

When normally closed high fire contacts 40-2 are opened due to the aforementioned energization of heater 40, the energizing path for by-pass valve solenoid 58 is interrupted, thus closing valve 52 to close the hydraulic bypass of fuel from line 48 through valve 52 and back to 42, and thereby increasing the flow to valve 54 in accordance with the preset conditions of fuel pressure valve 44. By virtue of this increased fuel flow to the burner nozzle the burner flame is increased to its high fire condition.

The system will continue in its high fire condition until it is desired to shut off the heat e.g. as indicated by thermostat 24 or by manually opening switch 25. It will be noted that scavenger contacts 40-1 are open during the high fire stage by virtue of the energization of heater 40 and for the following reason. When the system is shut off, it will take approximately 75 seconds for high fire and scavenger heater 40 to cool off sufliciently, to release scavenger contacts 40-1 to their normally closed position. During this cool-off period, there will be no available energizing circuit for motor relay coil 28, since pole 74 will have been returned to cold contact 66 and scavenger contacts 40-1 will be open. Accordingly, the low-fire stage could not be initiated during this cool-off period, which is necessary to allow the various heaters and thermistors in the relay control circuit to return to their initial ambient temperature conditions. Thus, since the cool-off time for scavenger heater 40 is substantially larger than the cool-off time for thermistor 92, an adequate pre-purge period, which corresponds to the heat up time for thermistor 92, is thereby assured.

An essential feature of the present invention is thus demonstrated in the provision of an inexpensive two stage burner control system having a fail-safe capability comprising a relatively simple and reliable relay control circuit utilizing'standard components. The above described preferred embodiment of the present invention is'deemed to be advantageous over presentlyavailable fuel burner controls, because circuits for controlling a two-stage fuel burner used heretofore have invariably required the use of a multiplicity of complicated and expensive circuitry components without being able to achieve the high degree of safety and reliability attained by the preferred embodiment of the present invention.

While there has been shown a particular embodiment of the present invention, it will be understood that it is not wished to be limited thereto, since modifications can be made both in the circuit arrangement and in the instrumentalities employed, and it is contemplated in the appended claims to cover any such modification as falls within the true spirit and scope of this invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A control system for a fuel burner having a nozzle, a source of fuel under pressure, and means for igniting said fuel when leaving said burner nozzle, said control system comprising fuel pump means for providing a supply of fuel from said fuel source to said burner nozzle; relay control means adaptable to be connected to an electrical power source having a pair of output terminals; valve means in circuit with said relay control means and operative in response thereto for controlling said fuel pump means for selectively providing a first level of fuel flow to said burner nozzle corresponding to a low-fire burner condition, and a second level of fuel flow to said burner nozzle greater than said first level corresponding to a highfire burner condition; an ignition transformer adaptable to being selectively connected to an electrical power source having a pair of output terminals for providing a voltage to energize said fuel ignition means; fail safe means operative to allow the establishment of said high-fire burner condition only upon the prior establishment of said lowfire burner condition, said fail safe means comprising flame detection means for detecting said low-fire condition; said pump means comprising a fuel pump having first and second suction inputs and a pressure output, an input fuel line adaptable to be connected from said source of fuel to said first suction input, an output fuel line connected to said pressure output, a feedback fuel line connccted between said output fuel line and said second suction input, and a nozzle fuel line connected to said burner nozzle from the junction of said output fuel line and said feedback fuel line; said valve means comprising a first normally closed valve disposed in said feedback line, said first valve being operative in response to said relay control means to selectively vary the magnitude of fuel flow from said output fuel line to said second suction input, and a second valve disposed in said nozzle fuel line to selectively vary the magnitude of the fuel flow from said output fuel line to said burner nozzle to thereby control the magnitude of the burner flame.

2. A control system for a fuel burner as defined in claim 1 wherein said valve means includes a regulating valve located at said pressure output for regulating the fuel pressure in said output fuel line.

3. A control System for a fuel burner as defined in claim 1 wherein said valve means further includes a pressure relief valve connected at the junction of said fuel output line and said feedback line, said pressure relief valve be ing operative to maintain the fuel flow in said feedback line at a preselected pressure.

4. A control system for a fuel burner as defined in claim 1 wherein said relay control means comprises a safety relay heater and a pair of associated normally closed contacts, a high fire and scavenger relay heater and its associated normally closed high-fire contacts and normally closed scavenger contacts, a double throw flame relay having a coil and associated first and second contacts, a transformer adaptable to being connected across a pair of A.C. power source output terminals, said transformer comprising a primary and a center-tapped secondary winding, a first relay having a coil and first, second and third pairs of associated contacts, a thermostatic switch serially interconnecting said first relay coil and said transformer secondary Winding, such that upon the closing of said thermostatic switch there is established an energizing circuit for said first relay comprising, the transformer secondary winding, the pole of said flame relay connected to its said first contact, said safety relay heater filament, said normally closed scavenger contacts, said normally closed safety relay contacts, said first relay coil, said thermostatic switch in its closed condition and said transformer winding.

5. A control system for a fuel burner as defined in claim 4 wherein said fuel pump means further includes a motor for driving said fuel pump, said motor having a pair of input terminals adapted to be connected to an electrical power source, and said relay control means includes means for energizing said pump motor and said ignition transformer comprising a second relay comprising a coil and a pair of associated contacts, said contacts interconnecting one of said A.C. source output terminals with one of said motor input terminals together with one of said ignition transformer input terminals, said second relay coil having one end thereof connected to the other of said A.C. source ouput terminals, said other of said A.C. source output terminals also being connected to the other of pump motor and ignition transformer input terminals, time delay means connected at one of its ends to the other end of said relay coil, and switching means connected between the other end of said time delay means and said one A.C. source output terminal.

6. A control system for a fuel burner as defined in claim 5 wherein said time delay means comprises a thermistor.

7. A control system for a fuel burner as defined in claim 6 wherein said switching means comprises said third pair of contacts associated with said first relay.

8. A control system for a fuel burner as defined in claim 4vwherein said valve means comprises first valve control means for controlling said first valve and second valve control means for controlling said second valve; said second valve control means comprising a second valve control solenoid connected at one of its ends to said other of said A.C. source output terminals, time delay means connected to one of its ends to the other end of said first valve control solenoid, switching means con nected between said one A.C. source terminal and the other end of said time delay means, said switching means being operative to complete an energizing circuit for said second valve control solenoid to thereby open said second valve at a time lagging the completion of said energizing circuit determined by said time delay means thereby providing a fuel flow in said burner nozzle fuel line at a level corresponding to said low-fire stage.

9. A control system for a fuel burner as defined in claim 8 wherein said time delay means comprises a thermistor.

10. A control system for a fuel burner as defined in claim 9 wherein said switching means comprises said third pair of contacts associated with said first relay.

11. A control system for a fuel burner as defined in claim 8 wherein said first valve control means comprises a first valve control solenoid connected at one end of its ends to said other of said A.C. source output terminals, a normally closed switch connected at one of its ends to the other end of said first valve control solenoids, switching means connected between the other end of said normally closed switch and said one A.C. source output terminals, said switching means being operative to complete an energizing circuit for said first valve control solenoid.

12. A control system for a fuel burner as defined in claim 11 wherein said switching means comprises said third pair of contacts associated with said first relay.

13. A control system for a fuel burner as defined in claim 12 wherein said. normally closed switch comprises said normally closed high-fire relay contacts.

14. A control system for a fuel burner as defined in claim 11 wherein said fail safe means includes light detection means operative in response to the impingement of light thereon to vary its impedance inversely with respect to the magnitude of said impinging light, said secondary winding being connected to a second series circuit comprising said flame relay coil and said light detection means, said flame relay being operative in response to a decrease in the impedance of said light detection means to cause the pole of said flame relay to make contact with its said second contact to thereby connect said secondary winding to a third series circuit comprising said flame relay pole, said flame relay second contact, said first relay second pair of contacts in their closed position, said high-fire and scavenge-r heater filament, said normally closed safety heater contacts, said first relay coil and said thermostatic switch, thereby causing said normally closed high-fire contacts to open to interrupt said series energizing circuit for said first valve solenoid to cause said normally closed first valve to close and thereby increase the flow of fuel to said burner nozzle to establish said highfire stage.

15. A control system for a fuel burner as defined in claim 14 wherein said light detection means comprises a cadmium cell operative to detect the magnitude of the light produced by said burner flame.

References Cited UNITED STATES PATENTS 1,862,690 6/193'2, M-acrae et al. 15828 2,022,879 12/1935 Carlberg 158-28 2,117,021 5/1938 Cotea 158--28 2,179,846 11/1939 Finnigan 158 28 10 2,979,124 4/1961 Kirk 158 28 JAMES W. WESTHAVER, Primary Examiner. 

1. A CONTROL SYSTEM FOR A FUEL BURNER HAVING A NOZZLE, A SOURCE OF FUEL UNDER PRESSURE, AND MEANS FOR IGNITING SAID FUEL WHEN LEAVING SAID BURNER NOZZLE, SAID CONTROL SYSTEM COMPRISING FUEL PUMP MEANS FOR PROVIDING A SUPPLY OF FUEL FROM SAID FUEL SOURCE TO SAID BURNER NOZZLE; RELAY CONTROL MEANS ADAPTABLE TO BE CONNECTED TO AN ELECTRICAL POWER SOURCE HAVING A PAIR OF OUTPUT TERMINALS; VALVE MEANS IN CIRCUIT WITH SAID RELAY CONTROL MEANS AND OPERATIVE IN RESPONSE THERETO FOR CONTROLLING SAID FUEL PUMP MEANS FOR SELECTIVELY PROVIDING A FIRST LEVEL OF FUEL FLOW TO SAID BURNER NOZZLE CORRESPONDING TO A LOW-FIRE BURNER CONDITION, AND A SECOND LEVEL OF FUEL FLOW TO SAID BURNER NOZZLE GREATER THAN SAID FIRST LEVEL CORRESPONDING TO A HIGHFIRE BURNER CONDITION; AN IGNITION TRANSFORMER ADAPTABLE TO BEING SELECTIVELY CONNECTED TO ELECTRICAL POWER SOURCE HAVING A PAIR OF OUTPUT TERMINALS FOR PROVIDING A VOLTAGE TO ENERGIZE SAID FUEL IGNITION MEANS; FAIL SAFE MEANS OPERATIVE TO ALLOW THE ESTABLISHMENT OF SAID HIGH-FIRE BURNER CONDITION ONLY UPON THE PRIOR ESTABLISHMENT OF SAID LOWFIRE BURNER CONDITION, SAID FAIL SAFE MEANS COMPRISING FLAME DETECTION MEANS FOR DETECTING SAID LOW-FIRE CONDITION; SAID PUMP MEANS COMPRISING A FUEL PUMP HAVING FIRST AND SECOND SUCTION INPUTS AND A PRESSURE OUTPUT, AN INPUT FUEL LINE ADAPTABLE TO BE CONNECTED FROM SAID SOURCE OF FUEL TO SAID FIRST SUCTION INPUT, AN OUTPUT FUEL LINE CONNECTED TO SAID PRESSURE OUTPUT, A FEEDBACK FUEL LINE CONNECTED BETWEEN SAID OUTPUT FUEL LINE AND SAID SECOND SUCTION INPUT, AND A NOZZLE FUEL LINE CONNECTED TO SAID BURNER NOZZLE FROM THE JUNCTION OF SAID OUTPUT FUEL LINE AND SAID FEEDBACK FUEL LINE; SAID VALVE MEANS COMPRISING A FIRST NORMALLY CLOSED VALVE DISPOSED IN SAID FEEDBACK LINE, SAID FIRST VALVE BEING OPERATIVE IN RESPONSE TO SAID RELAY CONTROL MEANS SELECTIVELY VARY THE MAGNITUDE OF FUEL FLOW FROM SAID OUTPUT FUEL LINE TO SAID SECOND SUCTION INPUT, AND A SECOND VALVE DISPOSED IN SAID NOZZLE FUEL LINE TO SELECTIVELY VARY THE MAGNITUDE OF THE FUEL FLOW FROM SAID OUTPUT FUEL LINE TO SAID BURNER NOZZLE TO THEREBY CONTROL THE MAGNITUDE OF THE BURNER FLAME. 